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Weather and Climate Dynamics An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/wcd-2020-8
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wcd-2020-8
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 19 Mar 2020

Submitted as: research article | 19 Mar 2020

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This preprint is currently under review for the journal WCD.

The American Monsoon System in HadGEM3.0 and UKESM1 CMIP6 simulations

Jorge L. García-Franco1, Lesley J. Gray1,2, and Scott Osprey1,2 Jorge L. García-Franco et al.
  • 1Atmospheric, Oceanic and Planetary Physics, Department of Physics. University of Oxford
  • 2National Centre for Atmospheric Science, UK

Abstract. The simulated climate in the American Monsoon System (AMS) in the CMIP6 submissions of HadGEM3.0 GC3.1 and the UKESM1 is assessed and compared to observations and reanalysis. Pre-industrial control and historical experiments are analysed to evaluate the model representation of this monsoon under different configurations, resolutions and with and without Earth System processes. The simulations exhibit a good representation of the temperature and precipitation seasonal cycles, although the historical experiments overestimate summer temperature in the Amazon, Mexico and Central America by more than 1.5 K. The seasonal cycle of rainfall and general characteristics of the North American Monsoon are well represented by all the simulations. The models simulate the bimodal regime of precipitation in southern Mexico, Central America and the Caribbean known as the midsummer drought, although with a stronger intraseasonal variation than observed. Austral summer biases in the modelled Atlantic Intertropical Convergence Zone (ITCZ), Walker Circulation, cloud cover and regional temperature distributions are significant and influenced the simulated spatial distribution of rainfall in the South American Monsoon. These biases lead to an overestimation of precipitation in southeastern Brazil and an underestimation of precipitation in the Amazon. El Niño Southern Oscillation (ENSO) characteristics and teleconnections to the AMS are well represented by the simulations. The precipitation responses to the positive and negative phase of ENSO in subtropical America are linear in both pre-industrial and historical experiments. Overall, the UKESM has the same performance as the lower resolution simulation of HadGEM3.0 GC3.1 and no significant difference for the AMS was found between the two model configurations. In contrast, the medium resolution HadGEM3.0 GC3.1 N216 simulation outperforms the low-resolution simulations in temperature, rainfall, ITCZ and Walker circulation biases.

Jorge L. García-Franco et al.

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Jorge L. García-Franco et al.

Jorge L. García-Franco et al.

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Latest update: 07 Apr 2020
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Short summary
The American Monsoon System is the main source of rainfall for the subtropical Americas and an important element of Latin American agriculture. Here we use state-of-the-art climate models from the UK Met Office in different configurations to analyze the performance of these models in the American Monsoon. Resolution is found to be a key factor to improve monsoon representation whereas integrated chemistry does not improve the simulated monsoon.
The American Monsoon System is the main source of rainfall for the subtropical Americas and an...
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